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Sources of CPU interference in core Linux code

Linux version: 3.3

CPU interference: For the the purpose of this document, CPU interference is defined as any case where kernel management functions will take CPU time from a pure CPU bound user task making no system call and running pinned to an isolated CPU with no other contending user tasks. Specifically, any kernel activity that occurred as a result of the the specific task activity is not considered interference. However, kernel activity on the specific CPU happening as a result of work of other tasks or the general kernel infrastructure not related a specific task are considered interference.

Global IPIs

fs/buffer.c - Global IPI for each LRU drain [1]

kernel/hrtimer - Global IPI for setting high res-timer when system clock is changed [2]

Only relevant if your clock source is not stable. Can be turned off by a CONFIG option, which is currently hard coded to true for x86. This patch allows is to be turned off: https://lkml.org/lkml/2012/3/27/193.